1. Field of Invention
The invention relates generally to the field of non-destructive testing. More specifically, the present invention relates to a method and system for spectroscopic analysis using a laser-ultrasound system.
2. Description of Prior Art
Recent developments in creating composite materials have expanded the use of composite materials into a wide variety of applications. Because of its high strength and durability combined with its low weight, composites are replacing metals and metal alloys as the base material for certain load bearing components. For example, composites are now commonly used as a material for body parts and structure in vehicles such as automobiles, watercraft, and aircraft. However, to ensure composite mechanical integrity, strict inspections are required. The inspections are typically required upon fabrication of a component made from a composite and periodically during the life of the component.
Laser ultrasound is one example of a method of inspecting objects made from composite materials. The method involves producing ultrasonic vibrations on a composite surface by radiating a portion of the composite with a pulsed generation laser. A detection laser beam is directed at the vibrating surface and scattered, reflected, and phase modulated by the surface vibrations to produce phase modulated light. Collection optics receives the phase modulated laser light and directs it for processing. Processing is typically performed by an interferometer coupled to the collection optics. Information concerning the composite can be ascertained from the phase modulated light processing, the information includes the detection of cracks, delaminations, porosity, foreign materials (inclusions), disbonds, and fiber information.
One of the advantages of using laser ultrasound for objects with a complex shape, such as components used in aerospace, is a couplant is unnecessary and the complex shaped can be examined without contour-following robotics. Laser-ultrasound can be used in aerospace manufacturing for inspecting polymer-matrix composite materials. These composite materials may undergo multiple characterization stages, one of which is the ultrasonic inspection by laser-ultrasound. At some point during manufacturing these composites must be chemically characterized to ensure the resins used in forming the composite are properly cured. Additionally, it is important to determine that the correct resins were used in the forming process. Composite chemical characterization typically involves obtaining control samples for infrared spectroscopy laboratory analysis.